An apparatus of this type is disclosed in German Patent Disclosure DE 31 45 342 A1. In order to have the capability at little expense and without disruption of introducing the broadest possible range of different impregnating agents into the individual yarns of the yarn sheet, the impregnating agent or sizing is introduced immediately upstream of and into the gap between each pairs of rollers, where it penetrates the yarns and at the same time is metered in its amount per unit of length of the yarn sheet by means of the roller gap. In an exemplary embodiment, a pair of rollers with a common vertical tangent is followed along the transport path of the yarn sheet by a pair of rollers with a common horizontal tangent. In the area upstream of the particular gap between each pair of rollers (as viewed in the of the direction of travel of the yarn sheet), the sizing is introduced from a supply line aimed into the gap and/or from a trough into which one roller dips. With this known squeezing-type sizing applicator, hot, low-concentration sizing can be applied to the yarns in a warp.
Recently, however, an attempt has been made to use highly concentrated sizings as well, for instance in order to reduce the expenditure of energy in the ensuing drying operation. For this situation, it is proposed in German Patent Disclosure DE 41 18 076 A1 that application of the sizing be accomplished by moving the yarn sheet past a first sizing applicator roller, which contacts one side of the yarn sheet essentially at a tangent over a limited circumferential range, and then moving the yarn sheet with its opposite side past a second sizing applicator roller, again contacting it essentially at a tangent over a limited circumferential range, thus subjecting the yarn sheet to a slop-pad type treatment on both faces. The yarn sheet is then dried and finally wound, for instance onto a warp beam. As contrasted to the aforementioned squeezing-type sizing applicator, the machine just described will be referred to hereinafter as a slop-pad sizing applicator.
In the textile industry, there are warp yarn sheets (or other sheet articles) that can be adequately well-sized with the aid of slop-pad treatment, but there are also warp yarn sheets that can be properly penetrated with the applicable sizing only in a more conventional way, i.e. by means of a dipping and squeezing treatment. The manufacturer who wishes to be able to treat both types of article or yarn sheets must therefore have both squeezing units and slop-pad units available in the manufacturing plant to be used as alternatives, which above all presents considerable problems.